Large Superluminous Areas on W UMa Systems. II. YZ Phoenicis

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Session 85 -- Interacting Binaries: ``Normal'' Stars
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[85.07] Large Superluminous Areas on W UMa Systems. II. YZ Phoenicis

R. Samec and J. Gray (Millikin University Department of Physics and Astronomy), D. Terrell (Dept. of Astronomy, University of Florida), M. Arruda (J.I. Holcomb Observatory, Butler University)

A photometric analyses of B,V,Rc,Ic light curves of the very short period period (P = 0.235d) W UMa binary, YZ Phe, is reported. The photometry was done in November 1989 using the 1-meter telescope at Cerro Tololo InterAmerican Observatory with a dry-ice-cooled Hamamatsu R943-02 Gs-As PMT. A large O'Connell effect is present in the light curves with the maximum following primary eclipse 0.1 mag brighter in B than the maximum following the secondary. A brief ~15 minute interval of constant light is discernable in the primary eclipse indicating that the more massive component is the cooler. The new version of the Wilson code (1992) was used to analyze the system with both a first and second order reflection effect. The four color simultaneous solution strongly suggests the presence of a large 56 degree radius superluminous region on the cooler component with a temperature factor of only 1.03. Further, we find that the system consists of a late G and an early K spectral type dwarfs in marginal contact, fillout ~ 4%, with a mass ratio of O.39. This research represents the first published solution for YZ Phe and was partially supported by a grant from NASA administered by the American Astronomical Society.

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